Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$239.39	5.820%	$253.3225	$253.32	$253.30	$253.30
Purchase #2	$137.97	12.661%	$155.4384	$155.44	$155.45	$155.40
Purchase #3	$62.61	7.160%	$67.0929	$67.09	$67.10	$67.10
Purchase #4	$90.41	10.761%	$100.139	$100.14	$100.15	$100.10
Purchase #5	$106.55	7.807%	$114.8684	$114.87	$114.85	$114.90
Purchase #6	$160.40	12.608%	$180.6232	$180.62	$180.60	$180.60
Purchase #7	$154.37	4.565%	$161.417	$161.42	$161.40	$161.40
7 purchase totals =	$951.70		$1,032.9014	$1,032.90	$1,032.85	$1,032.80